Power converter with capacitive energy transfer and fast dynamic response
A converter circuit and related techniques for providing high power density power conversion includes a reconfigurable switched capacitor transformation stage coupled to a magnetic converter (or regulation) stage. The circuits and techniques achieve high performance over a wide input voltage range or a wide output voltage range. The converter can be used, for example, to power logic devices in portable battery operated devices.
1. A converter circuit comprising:
a switched capacitor transformation stage having a transformation stage input port and a transformation stage output port, said switched capacitor transformation stage comprising one or more switches and one or more capacitors and said switched capacitor transformation stage configured to accept an input voltage V IN at the transformation stage input port and provide an intermediate output voltage at the transformation stage output port;
an auxiliary converter stage having an input coupled to said switched capacitor transformation stage, said auxiliary converter stage comprising one or more switches and one or more magnetic energy storage components configured to recover energy normally dissipated in capacitors of said switched capacitor transformation stage via said one or more magnetic energy storage components;
wherein in response to the one or more switches of said switched capacitor transformation stage being configured so that a capacitor in said switched capacitor transformation stage is charging or discharging, said switched capacitor transformation stage operates such that a portion of the difference between the input voltage V IN and a capacitor stack voltage V c appears across the input of said auxiliary converter stage and said auxiliary converter stage recovers energy normally dissipated when charging or discharging capacitors of said switched capacitor transformation stage;
wherein the portion of the difference between the input voltage VIN and the capacitor stack voltage V c corresponds to a majority of the difference between the input voltage V IN and the capacitor stack voltage V c ;
wherein said one or more switches in said auxiliary converter stage operate at a switching frequency which is higher than the switching frequency of the one or more switches in said switched capacitor transformation stage.
2. The converter circuit of claim 1 wherein the input of said auxiliary converter stage is provided having an apparent input resistance which is higher than an equivalent series resistance of said switched-capacitor transformation stage.
3. The converter circuit of claim 1 wherein at least one of said one or more magnetic energy storage components comprises an inductive element.
4. The converter circuit of claim 1 wherein said switched capacitor transformation stage is provided as a reconfigurable switched capacitor transformation stage which provides power conversion at multiple distinct conversion ratios.
5. The converter circuit of claim 1 wherein said switched capacitor transformation stage provides power conversion as a function of at least one of: an input voltage V IN , a reference voltage, the intermediate voltage, and an output voltage.
6. The converter circuit of claim 1 wherein in response to said one or more switches in said switched capacitor transformation stage being configured so that the capacitor is charging, the input voltage V IN and the capacitor stack voltage V c appears across the input of said auxiliary converter stage.
7. The converter circuit of claim 1 wherein in response to said one or more switches of said switched capacitor stage being configured such that a capacitor in said switched capacitor transformation stage is discharging, said switched capacitor transformation stage operates such that a portion of the difference between the input voltage V IN and a capacitor stack voltage V c appears across the input of said auxiliary converter stage.
8. The converter circuit of claim 1 wherein said switched capacitor transformation stage operates such that a portion of the difference between the input voltage V IN and a capacitor stack voltage V c appears across the input of the auxiliary converter stage in response to a change in charge in at least one capacitor of said switched capacitor transformation stage.